Precious stones, also known as gemstones, are rare and valuable minerals that are often cut and polished for use in jewelry. Common examples include diamonds, rubies, sapphires, and emeralds. These stones are prized for their beauty, durability, and rarity, making them highly sought after in various cultures around the world. The value of precious stones is determined by factors such as color, clarity, cut, and carat weight, often referred to as the "Four Cs." Additionally, some gemstones, like opals and tanzanite, are considered semi-precious but can still be quite valuable depending on their quality and demand.